Report on Aira (Japan) — September 1997
Bulletin of the Global Volcanism Network, vol. 22, no. 9 (September 1997)
Managing Editor: Richard Wunderman.
Aira (Japan) Relatively quiet but an 11 May explosion sent bombs hundreds of meters down the flanks
Please cite this report as:
Global Volcanism Program, 1997. Report on Aira (Japan). In: Wunderman, R. (ed.), Bulletin of the Global Volcanism Network, 22:9. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199709-282080.
31.593°N, 130.657°E; summit elev. 1117 m
All times are local (unless otherwise noted)
During February-May 1997, the volcano was relatively quiet with occasional small explosions and B-type earthquakes; during March and April, seismic activity was moderate. On 11 May, an explosion of much smaller magnitude than the 14 December 1996 event (BGVN 22:01) created a detectable air-shock and projected bombs 40% of the way down the volcano's slope. The Sakurajima Volcanological Observatory reported increasing A-type earthquakes for a few months before the explosion.
Geologic Background. The Aira caldera in the northern half of Kagoshima Bay contains the post-caldera Sakurajima volcano, one of Japan's most active. Eruption of the voluminous Ito pyroclastic flow accompanied formation of the 17 x 23 km caldera about 22,000 years ago. The smaller Wakamiko caldera was formed during the early Holocene in the NE corner of the Aira caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim of Aira caldera and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4850 years ago, after which eruptions took place at Minamidake. Frequent historical eruptions, recorded since the 8th century, have deposited ash on Kagoshima, one of Kyushu's largest cities, located across Kagoshima Bay only 8 km from the summit. The largest historical eruption took place during 1471-76.
Information Contacts: Sakurajima Volcanological Observatory (SVO), Kyoto University; Volcanological Division, Japan Meteorological Agency (JMA), 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100, Japan.